Research to solve a number of important structural problems in protein chemistry and to continue the development of instrumentation and methodology for the ultra high sensitivity sequence analysis of proteins by tandem mass spectrometry is proposed. Efforts will be made: (a) to implement a subtractive Edman degradation scheme that can be used to sequence small proteins or mixtures of peptides adsorbed onto microcapillary chromatography columns interfaced directly to the electrospray ionization source on a triple quadrupole mass spectrometer; (b) to develop sequential microcapillary chromatography/triple quadrupole mass spectrometry for protein isolation, enzymatic degradation, peptide fractionation, and sequence analysis at the femtomole level (c) to reduce the amount of sample required for sequence analysis of peptides on our existing triple quadrupole mass spectrometer to the subfemtomole level; (d) to sequence the target proteins and to define the binding sites for the anticancer drug, mimosine; (e) to characterize the posttranslational modifications required for activation of virulence factors in bacteria such as Bordetella pertussis (whooping cough) and pathogenic Escherichia coli, (f) to sequence a negative transcription regulator protein that blocks the antiproliferative effect of interferons and may be involved in the development of malignancy; (g) to define the domains of interaction between components of the G protein heterotrimeric complex and both the adenosine A/1 receptor and the effector protein, phospholipase C; (h) to continue studies to identify and sequence protein kinases involved in the signal transduction pathway activated by binding of insulin to its cell surface receptor; (i) to continue studies to elucidate posttranslational modifications found on neuronal tubulins; (j) to initiate studies with combinatorial peptide libraries to selectively isolate and characterize, proteins with specific protein binding motifs.